GCSEScienceWJECScience (Double Award)ChemistryExam QuestionsChemical Substances, Reactions & Essential ResourcesAtomic Structure & The Periodic Table

Atomic Structure & The Periodic Table (WJEC GCSE Science (Double Award): Chemistry): Exam Questions

Exam code: 3430

3 hours34 questions

3 marks

The diagram shows part of the Periodic Table. The letters A–F are not the chemical symbols of the elements.

Figure: Outline of part of the Periodic Table drawn as a grid of blank element boxes across five rows (periods), with a gap between the left-hand and right-hand blocks representing the transition metals region. Six specific element positions are marked with individual letters: A in the upper-right area (row 1), B in the far-left column (row 2), C in the second column from the left (row 3), D in the far-right column (row 3, same row as C), E right-of-centre (row 4), and F left-of-centre (row 5)

Use letters A–F to answer parts (i)–(iii).

(i) Give the letter of an element in Period 3.

.......................................................

[1]

(ii) Give the letter of an element in Group 2.

.......................................................

[1]

(iii) Give the letter of an element which is a non-metal.

.......................................................

[1]

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5 marks

Elements A, B, C, D and E are shown in the Periodic Table.

Figure: Periodic table diagram highlighting five unlabelled positions, marked A, B, C, D and E at different points across the periods and groups (not using the elements' real chemical symbols)

These letters are not the chemical symbols for the elements.

Give the letter of the element which fits each description below.

Description	Letter
is in Group 2	..................................
makes a 'pop' noise with a lit splint	..................................
has both metal and non-metal properties	..................................
reacts with lithium to make lithium chloride	..................................
is unreactive	..................................

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5 marks

The most common understanding of the term 'heavy metal' is a metallic element which is toxic and has a high density, atomic number and relative atomic mass. The definitions used vary depending on the context. In metallurgy, for example, a heavy metal is defined on the basis of density, whereas in physics the distinguishing factor is atomic number. A chemist would likely be more concerned with chemical behaviour. More specific definitions have been published but none of these have been widely accepted.

Despite this lack of agreement, the term is widely used in science. Heavy metals are sometimes defined as metals with a density greater than 5 g/cm³. They are often highly toxic or damaging to the environment. Chromium, arsenic, cadmium, mercury and lead have the greatest potential to cause harm on account of their extensive use.

Heavy metals are dangerous because they tend to bio-accumulate. Bio-accumulation occurs when the toxic chemical is taken into the body faster than it can be excreted. Lead can have an adverse impact on mental development in infants and children. Lead may also be a factor in behavioural problems. Heavy metal poisoning could result, for instance, from drinking-water contamination.

Lead is the most prevalent heavy metal contaminant. As a component of tetraethyl lead, (CH₃CH₂)₄Pb, it was used extensively in 'leaded petrol' from the 1930s-1970s. Although the use of leaded petrol has been phased out, soils next to roads can have high lead concentrations – see Figure 1. Lead-based paints were another early source of lead pollution but their use is now banned in the UK. Figure 2 opposite shows how the amount of lead used in paint and petrol in the USA changed over the 20th century.

Figure 1

Bar chart of lead concentration against distance from a road centre: town values are 900, 850, 750, 500, 550, 400 and 500 ppm; countryside values are 200, 180, 170, 110, 100, 90 and 80 ppm at 12–42 metres.

Figure 2

Line graph of lead used in US paint and petrol from 1910–1990, measured in thousands of tonnes. Dotted paint falls to about zero by 1975; solid petrol peaks at about 250 in the early 1970s and reaches zero by 1990.

(i) Put a tick ( $✓$ ) in the box next to the statement which best describes why a single definition of a 'heavy metal' is not accepted by all scientists.

metallurgists, physicists and chemists do not trust each other	$□$
metallurgists, physicists and chemists are not concerned with the fact that heavy metals are toxic	$□$
metallurgists, physicists and chemists are concerned with different properties of heavy metals	$□$
metallurgists, physicists and chemists study different heavy metals	$□$

[1]

(ii) Since the 1970s the use of lead water pipes has been prohibited across Europe. Explain why this is the case.

[1]

(iii) Put a tick ( $✓$ ) in the box next to the two statements which describe the conclusions that can be drawn from the data in Figure 1.

lead contamination in road-side soil decreases in towns and in the countryside as the distance from the centre of the road increases	$□$
the decrease in lead contamination between 12 m and 42 m from the centre of the road is greater in towns than in the countryside	$□$
lead contamination in road-side soil at all distances is much greater in towns than in the countryside	$□$
lead contamination in road-side soil decreases between 12 m and 42 m from the centre of the road in the countryside	$□$
there is approximately 50% more lead contamination in road-side soil in towns compared to the countryside between 12 m and 28 m from the centre of the road	$□$
there is an overall decrease of nearly 70% in the lead contamination of road-side soil in towns between 12 m and 42 m from the centre of the road	$□$

[2]

(iv) In the mid-1970s the use of lead in paints and the manufacture of cars that used leaded petrol was banned. Put a tick ( $✓$ ) in the box next to the statement which best describes what happened after the ban.

paint and petrol were lead-free by the mid-1970s anyway	$□$
paint and petrol were not lead-free until 1980	$□$
the use of lead-based paint and leaded petrol increased until 1980 before decreasing	$□$
it took 15 years for paint and petrol to become lead-free	$□$

[1]

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21a

1 mark

The following information is about the Group 7 elements of the Periodic Table, called the halogens.

Periodic table diagram titled “Group 7 – the halogens”, with fluorine, chlorine, bromine, iodine and astatine shaded in the same vertical column; an arrow points to fluorine at the top.

The Group 7 elements all exist as diatomic molecules, meaning their atoms go around in pairs. Fluorine is found at the top of the group, astatine is at the bottom of the group.

Chlorine, atomic number 17, is a pale green gas at room temperature (20°C). It has a melting point of -101°C. Bromine, atomic number 35, is a red-brown liquid at room temperature. It has a melting point of -7°C. Iodine, atomic number 53, is a grey solid at room temperature. It has a melting point of 114°C.

Chlorine is used to make bleaches, to treat public drinking water and to sterilise public swimming pools. Bromine is used by gardeners in pesticides, to prevent insects from harming plants. Iodine solution is used as an antiseptic on wounds and on patients before being operated on.

Which one of these statements best describes the trend in the melting points of the Group 7 elements as you go down the group? Tick ( $✓$ ) the correct answer.

The melting point increases	$□$
The melting point decreases	$□$
The melting point increases and then decreases	$□$
There is no trend in the melting point	$□$

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21b

2 marks

Predict a value for the boiling point of chlorine and explain your answer.

Boiling point of chlorine .................................... °C

Explanation ...................................................................................................................................................................

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21c

1 mark

Give the property that the Group 7 elements have that means they can be used as described in the text.

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21d

2 marks

Decide whether the following statements about astatine are true or false.

Astatine ...	True/False
... is a solid at room temperature
... conducts electricity
... has a melting point higher than 114°C
... is coloured

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30a

2 marks

The table shows some properties of elements in Period 3 of the Periodic Table.

Element	Melting point (°C)	Boiling point (°C)	Density (g / cm³)	Appearance	Malleability	Conductivity
Na	98	882	1.00	shiny solid	malleable	good
Mg	650	1091	1.75	shiny solid	malleable	good
Al	660	2470	2.70	shiny solid	malleable	good
Si	1410	3265	2.35	shiny solid	brittle	semiconductor
P	44	281	1.80	red solid	brittle	poor
S	113	444	2.05	yellow solid	brittle	poor
Cl	−101	−34	0.003	green gas	n/a	poor

One of the elements is difficult to classify as a metal or non-metal.

Identify this element and give your reasoning.

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30b

2 marks

Tick (✓) two boxes which correctly describe the change in density and boiling point for the elements across Period 3.

The density of metals and non-metals increases	$□$
The boiling point of metals increases but the boiling point of non-metals shows no trend	$□$
The density of metals shows no trend but the density of non-metals decreases	$□$
The boiling point of metals and non-metals shows no trend	$□$
The density of metals increases but the density of non-metals shows no trend	$□$
The boiling point of metals shows no trend but the boiling point of non-metals decreases	$□$
The density of metals decreases but the density of non-metals shows no trend	$□$

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30c

1 mark

Argon is the next element in Period 3 after chlorine, Cl.

State why it is not possible to predict a melting point for argon using the information in the table.

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30d

3 marks

Phosphorus is found in phosphoric acid, H₃PO₄.

(i) During the production of phosphoric acid, phosphorus is heated to 60 °C.

Give the state of phosphorus at 60 °C. Explain your choice.

[2]

(ii) Phosphoric acid reacts with zinc to produce zinc phosphate and hydrogen.

Balance the equation for this reaction.

[ ]H₃PO₄ + [ ]Zn → Zn₃(PO₄)₂ + [ ]H₂

[1]

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Name of particle	Charge	Mass
proton	..................................	1
neutron	0	..................................
electron	-1	almost zero

Salt	Flame test	Silver nitrate test	Name of salt
A	lilac flame	yellow precipitate	............................
B	............................	no change	calcium nitrate
C	............................	...........................	barium bromide

Test	Observation
bubble the gas through limewater	limewater did not change
place a burning splint in the gas	a squeaky pop and the splint went out

Element	Sodium bromide	Sodium iodide	Sodium chloride
X	solution turns orange	solution turns brown	no change
Y	no change	no change	no change
Z	no change	solution turns brown	no change

Element	Melting point (°C)	Boiling point (°C)	Density (g / cm³)
lithium	181	1 330	0.53
sodium	98	883	0.99
potassium	64	759	0.86
rubidium	?	688	1.53
caesium	29	671	1.93

neither model has any neutrons	$□$
Thomson had electron shells in his model	$□$
Thomson did not think atoms are mostly empty space	$□$

electrons are in shells outside the nucleus	$□$
atoms have equal numbers of protons and electrons	$□$
atoms have equal numbers of protons and neutrons	$□$

electrons are outside the nucleus	$□$
electrons are inside the nucleus	$□$
there are more protons than electrons in an atom	$□$
protons are in a nucleus in the centre of an atom	$□$
atoms have particles with no charge	$□$

Ag⁺(aq) + Cl^-(aq) → AgCl(aq)	$□$
Ag⁺(s) + Cl^-(s) → AgCl(s)	$□$
Ag⁺(aq) + Cl^-(aq) → AgCl(s)	$□$
Ag⁺(s) + Cl^-(s) → AgCl(aq)	$□$

H⁺ + Cl^- → HCl	$□$
Ba²⁺ + SO₄^2- → BaSO₄	$□$
Ba²⁺ + S^2- + 4O^2- → BaSO₄	$□$
2H⁺ + 2Cl^- → 2HCl	$□$
Ba^2- + SO₄²⁺ → BaSO₄	$□$

Pair of solutions	Appearance of the reactants	Appearance when mixed	Temperature change when mixed
A	two colourless solutions	no change	increase
B	two colourless solutions	bubbles form	increase
C	two colourless solutions	white precipitate forms	no change
D	two colourless solutions	no change	no change

Particle	Number of protons	Number of neutrons	Number of electrons
A	14	14	14
B	19	20	18
C	15	16	18
D	16	16	16
E	11	12	11
F	12	12	10

Isotope	Atomic number	Mass number
1	......................	......................
2	......................	......................

Group 1 metal	Electronic structure	Group 2 metal	Electronic structure
sodium	2,8,1	magnesium	2,8,2
potassium	2,8,8,1	calcium	2,8,8,2

its density is 1.7 g/cm³	$□$
its melting point is 650 °C	$□$
it fizzes vigorously with sulfuric acid	$□$
it is malleable	$□$

Element	Melting point (°C)	Boiling point (°C)	Reaction with hot iron
fluorine	−220	−188	explosive
chlorine	−101	−34	very fast
bromine	−7	59	quite fast
iodine	114	......................	slow

Element	Electronic structure
A	2
B	2,6
C	2,8,1
D	2,8,7
E	2,8
F	2,8,6

it does not react with sulfuric acid	$□$
it is ductile	$□$
it would melt when it lands on planet J	$□$
its density is 11.3 g/cm³	$□$

it does not react with sulfuric acid	$□$
it is expensive	$□$
it is a good conductor of heat	$□$
it is non-magnetic	$□$
it has a melting point much higher than the temperature on planet J	$□$
it is shiny so will reflect the sun's rays	$□$

Element	Electronic structure	Group	Period
oxygen	2,6	6	2
chlorine	................................	7	3
................................................	2,8,5	5	3
potassium	2,8,8,1	1	.....................

Solid	Observations
Solid	Flame test	Silver nitrate test
A	apple-green flame	cream precipitate
B	red flame	white precipitate
C	yellow flame	yellow precipitate